The invention relates generally to imaging assemblies and more specifically to phosphor admixtures and phosphor screens for imaging assemblies.
Typically, for certain radiography systems, radiation (such as X-rays) is transmitted through an object and converted into light of corresponding intensity using a light production layer. Exemplary light production layers include phosphor screens. The light generated by the light production layer is provided to an electronic device. The electronic device is adapted to convert the light signals generated by the light production layer to corresponding electrical signals. The electrical signals are then used to construct an image of the object.
Radiography is performed using different radiation energies for different applications. Typically, industrial applications, such as nondestructive testing and baggage inspection applications, involve higher radiation energy levels than do medical applications. For high radiation energies (for example, above 1 MeV), phosphor screens can only capture adequate radiation when they have both a high atomic number and a sufficient thickness to absorb a large portion of the x-ray beams. However, heavy luminescent materials are typically inefficient emitters under x-rays. Accordingly, electron intensification is typically needed for high-energy (>150 kV) applications, whereas electron intensification is generally not needed for lower energy (<150 kV) applications. Moreover, the use of thicker screens reduces the spatial resolution of the resulting converted image.
Previous techniques to provide electron intensification include placing metallic plates in intimate contact with the phosphor screen. For this technique, electrons are deposited onto the phosphor, and electron intensification occurs. However, many of the electrons are trapped in the bulk of the metallic plate and thus do not intensify the phosphor screen. Additionally, the electrons may also be trapped in the support layer, typically a Mylar® layer, before reaching the active phosphor layer. Mylar ® is a registered tradename of DuPont Teijin Films.
It would therefore be desirable to provide an improved light production layer with electron intensification. It would further be desirable for the light production layer to be suitable for use with high energy radiation.